Convert CONFIG_SYS_MAXARGS to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_MAXARGS

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/mx7ulp_evk_defconfig b/configs/mx7ulp_evk_defconfig
index 12c89b5..b576039 100644
--- a/configs/mx7ulp_evk_defconfig
+++ b/configs/mx7ulp_evk_defconfig
@@ -17,6 +17,7 @@
 CONFIG_BOOTCOMMAND="mmc dev ${mmcdev}; if mmc rescan; then if run loadbootscript; then run bootscript; else if run loadimage; then run mmcboot; fi; fi; fi"
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_HUSH_PARSER=y
+CONFIG_SYS_MAXARGS=256
 CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_MEMTEST=y
 CONFIG_CMD_FUSE=y